Many different types of machines utilize hydraulic systems to operate work implements and hydrostatic drives. Examples of these machines include excavators, backhoes, loaders, haul trucks, and various other machines. The machines typically include a plurality of sensors and use closed-loop feedback systems to monitor the operation of the various systems within the machine.
Due to the complexity and size of the machines and to prevent undesired or uncontrolled operation, the systems are often configured to shut down or substantially reduce the performance of the machine upon the failure of a pressure or displacement sensor. In such case, productivity is lost while waiting for replacement of the inoperative sensor. In addition, additional sensors add to the cost and complexity of a machine.
U.S. Pat. No. 8,548,661 discloses a hybrid hydraulic excavator having an engine with both a variable displacement hydraulic pump and a motor generator connected to the engine. A controller is operative to determine a calculation value of the hydraulic pump based upon a pump current supplied to the pump and a discharge pressure of the pump using an algorithm, and corrects a hydraulic pump characteristic parameter used in the algorithm based upon an assumed pressure error. The controller further calculates an assumed hydraulic pressure correction output using the corrected hydraulic pump characteristic parameter, and controls the operation of the motor generator based upon the assumed hydraulic pressure correction output.
The foregoing background discussion is intended solely to aid the reader. It is not intended to limit the innovations described herein, nor to limit or expand the prior art discussed. Thus, the foregoing discussion should not be taken to indicate that any particular element of a prior system is unsuitable for use with the innovations described herein, nor is it intended to indicate that any element is essential in implementing the innovations described herein. The implementations and application of the innovations described herein are defined by the appended claims.